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  <script>
    // 需求  ["b", "c","b", "c","a", "b", "c"] 统计每个元素出现的次数,结果是： {a：1，b: 3, c:  3}
const arr = ["b", "c","b", "c","a", "b", "c"] 

const obj = arr.reduce(function(item,sum){
  console.log(item,sum);
  
},0)
// 你的代码 ...

console.log(obj) // ==> {a：1， b: 3, c:  3}
  </script>
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